Field of the Invention
The present invention relates to a sheet processing apparatus that has a function of aligning sheets stacked on a stack tray, and a control method for the sheet processing apparatus, and a storage medium.
Description of the Related Art
For sheet processing apparatuses that stack a large number of sheets, there has been demand for the ability to discharge and align the sheets with a high degree of accuracy. Japanese Patent Laid-Open No. 2006-206331 suggests a sheet alignment process in which alignment members (alignment mechanisms) are provided on a stack tray, and sheets are piled up in such a manner that the positions of edge surfaces of the sheets parallel to a sheet discharge direction are lined up by the alignment members coming into and out of contact with the edge surfaces of the sheets.
However, this conventional technique has the following problem. For example, when applying an alignment process to sheets newly stacked on printed materials (sheets) that are already stacked on a stack tray and have a different width from the newly-stacked sheets, the toner or ink on the already-stacked sheets could possibly be removed by the above alignment mechanisms coming into contact with the already-stacked sheets. This may lead to a reduction in the image quality of the printed materials.